Switched-mode Power Converters Research Articles

Multirate modeling and control design for switched-mode power converters

A class of pulse-width modulated (PWM) systems that includes many switched-mode power converters is considered. A new multirate low-frequency sampling PWM scheme is introduced that not only provides the possibility for new types of operation, but also unifies the switching logic corresponding to established PWM schemes. An exact nonlinear discrete-time model is used to develop multirate nonlinear controllers and observers based on map-inversion concepts. This nonlinear design methodology is widely applicable, requiring only that the continuous-time small-signal average model be controllable and observable. >

Spectral modeling of switched-mode power converters

A new modeling approach for the spectral analysis of pulsewidth modulated (PWM) converters with independent inputs is developed. The key of this approach is to extend the Volterra functional series to nonlinear systems with multiple independent inputs. After formulating the state-space equations describing the dynamical behavior of PWM converters, the Volterra transfer function characterizing the output frequency response can be obtained, which is then symmetrised to form the spectral model. Since the model is developed in a closed form, it is suitable for computer analysis. The modeling approach has been applied to various PWM converters, and the results are verified. The spectral models of different power converters can readily be obtained by using this general approach. >

Asymmetrical duty cycle permits zero switching loss in PWM circuits with no conduction loss penalty

It is shown that operating a bridge-type PWM switch mode power converter with asymmetrical duty ratios can eliminate switching losses with no increase in conduction loss. This circuit topology combines the best features of resonant (zero switching loss) and switch mode (low conduction loss) circuits. Design equations for the circuit are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of standards and power supply design options for limiting harmonic distortion in power systems

Harmonic distortion in power systems is growing due to the popularity of switch-mode power electronic equipment. This equipment has recognized advantages, such as reducing weight and improving control and efficiency in power converters and supplies. A disadvantage of switch-mode power converters is that their lowest-cost circuit may burden the power system with harmonic loading. Methods to reduce this distortion are recognized, but economic incentives are yet to be realized. Standardization is the most effective means to influence equipment design and to control distortion in power systems. The authors compare the major European and American standards, as well as some of the electronic equipment design changes that are supposed to limit harmonics. >

Synthesis of zero-impedance converter

A method for synthesizing a system that converts a finite value of an impedance to zero, with an associated finite current and zero voltage, is presented. The synthesis method comprises positive current feedback of an exactly specified nature and value of its transfer function. The stability and dynamics of the system are controlled by an additional voltage loop. The zero-impedance converter is used to synthesize load-independent systems including (switch-mode) power converters and electric motor drive systems incorporating any kind of motor. >

On the steady state analysis of switched mode power converters

On the steady state analysis of switched mode power converters

A Saturable Reactor Assisted Soft-Switching PWM DC-DC Converter.

In the demand for increasing power density of switched mode power converters, resonant topologies have attracted much attention because of their low switching losses and low EMI. However, they require relatively large resonant components, and high current or high voltage ratings for semiconductor devices.This paper presents a new soft-switching PWM full-bridge DC-DC converter which can overcome these drawbacks by utilizing a small saturable reactor. The principle of operation and steady-state characteristics are illustrated. The role of the saturable reactor is also discussed. Moreover, the voltage and current stresses for active and passive components are presented.To verify the results, key experiments were implemented with a 350W, 500kHz prototype converter. It is proved that the converter achieves soft-switching in a wide load range with no substantial increase in voltage and current stresses for active and passive components.

Performance potential of low-voltage power MOSFETs in liquid-nitrogen-cooled power systems

The performance potential of a power MOSFET in cryogenic power electronic systems is discussed. Based on a simple analysis and the measured performance of scaled silicided 30-V power MOSFETs, it is shown that an order of magnitude improvement in on-state resistance can be achieved by cooling to liquid-nitrogen temperature. This performance improvement results in an order of magnitude improvement in optimum power conversion frequency for a given die size, a factor of 2 reduction in die size at a given conversion frequency, and a factor of 3 reduction in total power loss for switched-mode power converters operated at 77 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A fast time-domain algorithm for the simulation of switching power converters

An efficient algorithm for the simulation of switched-mode power converters is developed. A Chebyshev series expansion is used to effectively solve the differential equations describing the system in each topology. The power of the new simulation technique lies both in the simple, but accurate, polynomial approximation for the state transition matrices and in the ability to explicitly obtain the instants at which the switching of the circuit topology takes place. The simulation technique is illustrated with reference to a simple Buck converter operating at a constant frequency. The derivation of the new algorithm is presented and its performance is analyzed. The case of a rapidly varying input forcing function is analyzed. Examples illustrating the generality and the computational efficiency of the algorithm are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Exact linearization in switched-mode DC-to-DC power converters

Three popular DC-to-DC switched mode power converters—Buck, Boost, and Buck-Boost—are shown to be in the same orbit of structural equivalence as a second-order controllable circuit in Brunovsky canonical form. The equivalence is achievable under non-linear feedback and explicit local difleomorphic state coordinate transformations. The implications of local exact linearizability of this class of systems in the design of Variable Structure Feedback Control laws or Pulse-Width-Modulation strategies is thoroughly discussed.

Sliding-mode control on slow manifolds of DC-to-DC power converters

In this article, general relationships are established among variable structure control strategies and pulse-width modulated control schemes leading to sliding modes in non-linear systems. The results are applied to the design of a sliding regime for the regulation of DC-to-DC switchmode power converters exhibiting a slow integral manifold due to time-scale separation properties among input and output circuits.

Small-signal modeling of pulse-width modulated switched-mode power converters

The state-space averaging method, associated with power converters, is discussed, Emphasis is on the motivation and objectives of modeling by equivalent circuits based on physical interpretation of state-space averaging. The discussion is limited to pulse-width-modulated DC-to-DC converters. >

Subharmonics and chaos in a controlled switched-mode power converter

A difference equation is derived for the output current, at successive switch events, of a simple switching-regulator DC/DC converter using a pulsewidth modulator. Wideband feedback control of the nonlinear circuit leads to a one-dimensional return map of zigzag form from which a stability criterion is found. Operation in the unstable region is described and verified by numerical simulation. The system exhibits a noisy bifurcation, chaos and subharmonics. >

Loss-free gyrator realization

A loss-free time-variable gyrator (TVG) based on the power-out-equals-power-in (POPI) concept is presented. The POPI is a 'black box' without source elements, in which the instantaneous output power equals the input. A method based on a controlled time-variable transformer is presented, and it is noted that based on the same method, transformer realization by means of a single-controlled gyrator can be achieved. Synthesis based on switched-mode power conversion circuits is discussed. A gyrator consisting of such a circuit has been constructed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sliding motions in bilinear switched networks

This article presents an application of variable structure systems theory, and the associated sliding regimes (Utkin [1]-[4]) of the systems, 1) to study energy transfers between dynamic storage elements in lossless bilinear networks and 2) to obtain a feasible reformulation of the constant regulation problem in dc-dc switch-mode power converters (SPC's) usually treated by approximate state-space averaging techniques on pulse width modulation (PWM) control schemes. The approach exploits the geometric aspects of the problems and obtains an analysis and design methodology, based on the ideal sliding mode qualitative characteristics, which is intuitively clear, mathematically feasible, and devoid of approximations.

Selecting the Optimum Switching Frequency for Switcher Design

A method for design optimization of switched-mode dc-dc power converters using bipolar transistors is formulated. Using the concept of multicriterion optimization, the optimum switching frequency is found on the basis of design tradeoffs amongst converter's efficiency, size, weight and cost.

Sliding Mode Control of Power Converters

Switched mode power converters are being used extensively for the purpose of efficient power conversion. Such converters are nonlinear, time variant systems. In the past such converters were being modelled using the state space averaging method. The theory of variable structure systems (VSS), and sliding mode control form a mutually complementary analysis and design tools for the control of switched mode power converters. The application of sliding mode control is presented for dc-to-dc converters and electrical motor drives in this thesis. The concept of sliding mode control is brought out through exhaustive examples of second order systems. The equivalent control, an analysis method of VSS, is applied to obtain transfer function description of dc-to-dc power converters. The sliding mode control is applied to the control problem of dc-to-dc power converters and speed controlled electrical drives to develop practical design techniques. The practical design methods are confirmed through experimental results.

A New Resonant Mode Amplifier Produces Clean AC Power

A new resonant mode power amplifier design is described which has a number of advantages over the power amplifiers available today. In particular, it has low or no EMI because of the nature of its operation. The new amplifier design is based upon a resonant mode dc-dc converter used in a push-pull configuration. All the advantages of the resonant mode power converters, such as high efficiency, small size and weight, excellent dynamic performance, low or no EMI (compared to PWM switch mode power converter), etc., are present in this new design.

Power Electronics in Space: A Review and Projection

Power electronics has emerged as a distinct field of electrical engineering in recent years. This emergence is closely linked with the development of power control and conversion equipment for space application over the last 20 years. Development of switched-mode power conversion techniques has been the dominant activity in this field, spurred by both the improvements in solid-state power devices and the needs of space systems for light weight, highly efficient techniques for dc power regulation. This history is reviewed and projections are made in the four key areas of circuit fundamentals, components, circuit practice, and applications.

Advances in Switched-Mode Power Conversion Part I

A new concept in the design of switched-mode power conversion circuitry is presented. Because of its extreme simplicity, flexibility, and efficiency, it has the potential to replace some conventional electrical power processing methods currently in use. A thorough discussion of the background, development, and operation of the ?uk converter and several of its extensions is included. The coupled-inductor technique further improves efficiency and reduces size and weight. The basic converter and its extensions to two-quadrant and four-quadrant operation are attractive for many applications, i.e., solar (dc) to utility line (ac) power conversion, variable speed dc or ac motor drives, switching power supplies, uninterruptible power supplies, and many others.